PerformanceLogger

The class that I use most is without a doubt PerformanceLogger. It does what the name implies, and is meant to be used like this:

//...
PerformanceLogger plog = new PerformanceLogger();
doWork();
plog.logElapsedAndRestart();
doSomeMoreWork();
plog.logElapsed();
//...

The implementation uses SLF4J. Varying with your logging configuration (PerformanceLogger logs to at.ipsquare.commons.core.util.PerformanceLogger with log level DEBUG), the code above will result in something like this written to your shiny logs:

17:52:33 PERFORMANCE SomeClass.someMethod[15->17] 333ms
17:52:33 PERFORMANCE SomeClass.someMethod[17->19] 222ms

If you happen to use LOGBack and you want your performance related log messages formatted similar to the example above, you might find the following logback.xml snippets useful:

<!-- ... -->
<property name="performancePattern" value="%d{HH:mm:ss} PERFORMANCE %msg%n"/>
<!-- ... -->
<appender name="PERFORMANCE_OUT" class="ch.qos.logback.core.ConsoleAppender">
  <encoder>
    <pattern>${performancePattern}</pattern>
  </encoder>
</appender>
<!-- ... -->
<logger name="at.ipsquare.commons.core.util.PerformanceLogger" level="DEBUG" additivity="false">
   <appender-ref ref="PERFORMANCE_OUT"/>
 </logger>
<!-- ... --> 

Note that you can simply turn of performance logging by setting the log level of at.ipsquare.commons.core.util.PerformanceLogger to anything above DEBUG. Also, you can create PerformanceLoggers that only generate output, if the elapsed time exceeds a certain threshold, and it is possible to enhance the loggers output with custom messages, like so:

PerformanceLogger plog = new PerformanceLogger(50);
doWork();
plog.logElapsed("Finally done");

If you are not content with the output that is produced by PerformanceLogger, or if you need something special, you can implement your own PerformanceLogFormatter. The defaults used by PerformanceLogger.PerformanceLogger() can be customized by adding an XML properties file called at/ipsquare/commons/core/util/performanceLogger.xml to the classpath. The recognized entries (which are all optional) are:

• defaultPerformanceLogFormatter: The fully qualified class name of a PerformanceLogFormatter implementation.
• defaultThreshold: The threshold in milliseconds.

Here is an example:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">

<properties>
    <entry key="defaultPerformanceLogFormatter">my.very.special.HandCraftedPerformanceLogFormatter</entry>
    <entry key="defaultThreshold">2</entry>
</properties>

Class and Resource Loading

• ClassLoaders is a global registry for class loaders that is used by all IP SQUARE commons components (this is especially true for LocalResources and Classes).
• LocalResources is an utility class for loading local resources from the classpath. You should use it whenever you want to load some data from the classpath, like default configurations, images packaged into a JAR file, or test data needed for unit tests.
• Classes is an utility class for class loading.

UnitOfWork

UnitOfWork represents some unit of work, that is typically, but not necessarily, executed by an UnitOfWorkExecutor implementation. Good examples of concrete UnitOfWork implementations are:

• Some code containing database operations that are meant to fail atomically.
• The processing of HTTP requests in a web application.
• The processing of SOAP/REST requests in a web service.
• A piece of code that should be executed with a different logging configuration.

Note that you should normally extend AbstractUnitOfWork instead of implementing UnitOfWork directly.

Miscellaneous

StackTrace contains utility methods around Thread.getStackTrace() that are used for implementing PerformanceLogger, but might as well be useful in another context. HasId and StringGenerator are two interfaces I employed successfully in multiple projects.